One characteristic of a turbine engine is that it includes rotating components carried by stationary components which absorb or are affected by forces generated by the rotating components. For example, in modern gas turbine engines, a rotating component or rotor comprises a variety of members such as shafts, shaft cones, disks or drums carrying blades, fluid seals, and various connecting structural members. At different points or portions in the engine, depending upon the relative pressure, thrust forces in the engine act axially on the engine. In the turbine portion of the engine in which gas stream or fluid flowpath pressures decrease axially downstream on the engine the net axial force is downstream. A compressor driven by a turbine can, to a certain extent, compensate for such net axial downstream force in the turbine: the highest pressure in the compressor is in its latter stages and tends to exert a net axial forward force. However, in a free wheeling power turbine, axial downstream force is absorbed by a thrust bearing or complex arrangement of bearings. State-of-the-art bearings can be used for ordinary gas turbines, including those with standard power turbines.
The gas turbine art, as it relates to industrial applications, has been advancing in one manner through the use of steam to improve thermal efficiency and increase output. Examples of such advances are U.S. Pat. No. 4,569,195--Johnson issued Feb. 11, 1986 and my U.S. Pat. No. 4,631,914 issued Dec. 30, 1986, the disclosures of both of which are hereby incorporated herein by reference. One result has been a significant increase in rotor thrust loads thereby requiring bearings of a capability presently unavailable.
Previously reported means for compensating for such high net axial thrust has been through the use of relatively high pressure air, bled from the compressor and applied to a portion of the engine. Another means, for example as described in U.S. Pat. No. 4,578,018--Pope, the disclosure of which is hereby incorporated herein by reference, utilizes hydraulic fluid for such purpose. However, use of air which the engine has compressed or hydraulic fluids such as used in the engine for lubricating purposes, can cause losses in engine efficiency.